4,6,37,38 In climbers ascending to very high altitudes, differences of a few days in acclimatization can have a significant impact on the prevalence of AMS, truly symptom severity, and mountaineering success.36 At 5,895 m, Kilimanjaro is the world’s highest free-standing mountain measured from base to summit. It is popular, easily accessible, and its location near the Inhibitors,research,lifescience,medical equator offers the option of combining a summit attempt with a

safari to neighboring game preserves. Every year 20,000 climbers try to reach the summit.6 The standard routes to the summit, with the possible exception of the Western Breech which requires some scrambling, are not technical and can potentially be hiked by anyone in good physical condition. In spite of the non-technical nature of the climb, there have been numerous fatalities on this mountain.6 To cut costs and compete effectively, Inhibitors,research,lifescience,medical trekking companies often schedule relatively rapid climbs leaving limited time for acclimatization. Of particular concern is the observation that some hikers continue to ascend in spite of developing life-threatening signs of high-altitude pulmonary or cerebral edema.6 Although not always practical, Inhibitors,research,lifescience,medical current recommendations are to limit the increase in sleeping altitude to 600 m in a 24-hour period

once above 2,500 m and to add an extra day of acclimatization for every 600–1,200 m gain in elevation. LATITUDE Latitude affects oxygen availability, hemoglobin saturation, and the risk of developing AMS. Due to its rotation, Inhibitors,research,lifescience,medical the Earth bulges at the equator; consequently, both barometric pressure and PO2 are higher at the equator than at the poles. On the 6,194 m summit of Denali in central Alaska, the barometric pressure is equivalent to barometric pressure on the summit of a 6,900-m peak in the Himalayas.39 Because of this effect, at an equivalent elevation climbers will be less Inhibitors,research,lifescience,medical hypoxic on Kilimanjaro (3°S) or even Everest (23°N) than on Denali (63°N). If Everest had

been situated at the same latitude as Denali, it could not have been climbed without Dacomitinib supplemental oxygen. GENDER AND AGE Men and women appear to be equally at risk for AMS,4,5,39 although some observational studies suggest a slightly higher risk for women.3 Older individuals do not appear to have an increased risk of AMS;4,36 in fact, one study suggests that younger individuals may be at higher risk. Eighteen-to-nineteen-year-olds had a 45% incidence of AMS at Colorado ski resorts compared to only 16% for those between 60 and 87 years of age.3 This study was uncontrolled, and the results are probably affected by a greater exercise intensity in the younger age group. There are no controlled trials of AMS in children, but the attack rate appears similar to that in adults.